Overcoming the matched-illumination challenge in Fourier ptychography microscopy with phase-contrast modulation

Fourier ptychography microscopy (FPM) is a powerful computational imaging technique; however, its performance is limited by the stringent matched-illumination requirement, especially when using high-numerical-aperture (NA) objective lenses. To address this challenge, we propose a phase-contrast modulation-based FPM (PCM-FPM). By introducing a 0.5π phase shift to the non-scattered components of object waves generated under unmatched illuminations from six LEDs, PCM-FPM encodes otherwise undetectable low-frequency phase information into measurable intensity variations. Then, a novel iterative reconstruction algorithm, to our knowledge, processes these six phase-contrast intensity images to recover full-spectrum phase details. Both simulations and experimental results, acquired with an illumination NA of 0.7 and a 100×/1.44 objective lens (OL), demonstrate the superior phase imaging performance of PCM-FPM. This approach represents a significant advancement in FPM with strong potential for broader application.